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Optimize duplicate vertices in DfgPeephole (#7305)

This commit is contained in:
Geza Lore 2026-03-21 22:45:02 +00:00 committed by GitHub
parent 13ceeb6add
commit 157fa9e4c5
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GPG Key ID: B5690EEEBB952194
4 changed files with 59 additions and 27 deletions
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4
src/V3Dfg.h
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@ -200,8 +200,6 @@ protected:
m_inputps.emplace_back(new DfgEdge{this});
return m_inputps.back().get();
}
// Unlink all inputs and reset to no inputs
void resetInputs() { m_inputps.clear(); }
public:
// Get input 'i'
@ -210,6 +208,8 @@ public:
void inputp(size_t i, DfgVertex* vtxp) { m_inputps[i]->relinkSrcp(vtxp); }
// The number of inputs this vertex has. Some might be unconnected.
size_t nInputs() const { return m_inputps.size(); }
// Unlink all inputs and reset to no inputs - use very carefully
void resetInputs() { m_inputps.clear(); }
// The type of this vertex
VDfgType type() const { return m_type; }

8
src/V3DfgCache.cpp
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@ -26,13 +26,15 @@
namespace V3DfgCacheInternal {
void V3DfgCache::cache(DfgVertex* vtxp) {
DfgVertex* V3DfgCache::cache(DfgVertex* vtxp) {
switch (vtxp->type()) {
#define VERTEX_CACHE_ADD_CASE(t) \
case t::dfgType(): V3DfgCacheInternal::cache(m_cache##t, reinterpret_cast<t*>(vtxp)); break;
case t::dfgType(): \
return V3DfgCacheInternal::cache(m_cache##t, reinterpret_cast<t*>(vtxp)); \
break;
FOREACH_CACHED_VERTEX_TYPE(VERTEX_CACHE_ADD_CASE)
#undef VERTEX_CACHE_ADD_CASE
default: break;
default: return nullptr;
}
}

32
src/V3DfgCache.h
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@ -254,26 +254,35 @@ inline Vertex* get(DfgGraph& dfg, T_Cache& cache, const DfgDataType& dtype, Oper
return it != cache.end() ? reinterpret_cast<Vertex*>(it->second) : nullptr;
}
// These add an existing vertex to the table, if an equivalent does not yet exist
inline void cache(CacheSel& cache, DfgSel* vtxp) {
// These add an existing vertex to the table. If an equivalent exists,
// it is returned and the cache is not updated.
inline DfgSel* cache(CacheSel& cache, DfgSel* vtxp) {
DfgSel*& entrypr = getEntry(cache, vtxp->dtype(), vtxp->fromp(), vtxp->lsb());
if (!entrypr) entrypr = vtxp;
if (entrypr && entrypr != vtxp) return entrypr;
entrypr = vtxp;
return nullptr;
}
inline void cache(CacheUnary& cache, DfgVertexUnary* vtxp) {
inline DfgVertexUnary* cache(CacheUnary& cache, DfgVertexUnary* vtxp) {
DfgVertexUnary*& entrypr = getEntry(cache, vtxp->dtype(), vtxp->inputp(0));
if (!entrypr) entrypr = vtxp;
if (entrypr && entrypr != vtxp) return entrypr;
entrypr = vtxp;
return nullptr;
}
inline void cache(CacheBinary& cache, DfgVertexBinary* vtxp) {
inline DfgVertexBinary* cache(CacheBinary& cache, DfgVertexBinary* vtxp) {
DfgVertexBinary*& entrypr = getEntry(cache, vtxp->dtype(), vtxp->inputp(0), vtxp->inputp(1));
if (!entrypr) entrypr = vtxp;
if (entrypr && entrypr != vtxp) return entrypr;
entrypr = vtxp;
return nullptr;
}
inline void cache(CacheTernary& cache, DfgVertexTernary* vtxp) {
inline DfgVertexTernary* cache(CacheTernary& cache, DfgVertexTernary* vtxp) {
DfgVertexTernary*& entrypr
= getEntry(cache, vtxp->dtype(), vtxp->inputp(0), vtxp->inputp(1), vtxp->inputp(2));
if (!entrypr) entrypr = vtxp;
if (entrypr && entrypr != vtxp) return entrypr;
entrypr = vtxp;
return nullptr;
}
// These remove an existing vertex from the cache, if it is the cached vertex
@ -357,8 +366,9 @@ public:
template <typename Vertex, typename... Operands>
inline Vertex* get(const DfgDataType& dtype, Operands... operands);
// Add an existing vertex of the table. If an equivalent already exists, then nothing happens.
void cache(DfgVertex* vtxp);
// Add an existing vertex of the cache. If an equivalent already exists,
// it is returned and the cache is not updated.
DfgVertex* cache(DfgVertex* vtxp);
// Remove an exiting vertex, it is the cached vertex.
void invalidateByValue(DfgVertex* vtxp);

42
src/V3DfgPeephole.cpp
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@ -170,22 +170,21 @@ class V3DfgPeephole final : public DfgVisitor {
}
void deleteVertex(DfgVertex* vtxp) {
// Add all sources to the work list
addSourcesToWorkList(vtxp);
// Inputs should have been reset
UASSERT_OBJ(vtxp->is<DfgVertexVar>() || !vtxp->nInputs(), vtxp,
"Operation Vertx should not have sources when being deleted");
// Should not have sinks
UASSERT_OBJ(!vtxp->hasSinks(), vtxp, "Should not delete used vertex");
// If in work list then we can't delete it just yet (as we can't remove from the middle of
// the work list), but it will be deleted when the work list is processed.
if (m_workList.contains(*vtxp)) return;
// Otherwise we can delete it now.
// Remove from cache
m_cache.invalidateByValue(vtxp);
// This pass only removes variables that are either not driven in this graph,
// or are not observable outside the graph. If there is also no external write
// to the variable and no references in other graph then delete the Ast var too.
const DfgVertexVar* const varp = vtxp->cast<DfgVertexVar>();
AstNode* const nodep
= varp && !varp->isVolatile() && !varp->hasDfgRefs() ? varp->nodep() : nullptr;
// Should not have sinks
UASSERT_OBJ(!vtxp->hasSinks(), vtxp, "Should not delete used vertex");
// Delete vertex and Ast variable if any
VL_DO_DANGLING(vtxp->unlinkDelete(m_dfg), vtxp);
if (nodep) VL_DO_DANGLING(nodep->unlinkFrBack()->deleteTree(), nodep);
@ -206,16 +205,30 @@ class V3DfgPeephole final : public DfgVisitor {
addSinksToWorkList(vtxp);
// Add replacement to the work list
addToWorkList(replacementp);
// Replace vertex with the replacement
// Add all sources to the work list
addSourcesToWorkList(vtxp);
// Remove this and sinks from cache
m_cache.invalidateByValue(vtxp);
vtxp->foreachSink([&](DfgVertex& sink) {
m_cache.invalidateByValue(&sink);
return false;
});
// Replace vertex with the replacement
vtxp->replaceWith(replacementp);
replacementp->foreachSink([&](DfgVertex& sink) {
m_cache.cache(&sink);
return false;
});
// Unlink and reset all inputs of the replaced vertex so it doesn't get iterated again
vtxp->resetInputs();
// Re-cache all sinks of the replacement, remove duplicates
while (true) {
DfgVertex* sinkp = nullptr;
DfgVertex* samep = nullptr;
replacementp->foreachSink([&](DfgVertex& sink) -> bool {
sinkp = &sink;
samep = m_cache.cache(&sink);
return samep;
});
if (!samep) break;
replace(sinkp, samep);
}
// Vertex is now unused, so delete it
deleteVertex(vtxp);
}
@ -1855,6 +1868,7 @@ class V3DfgPeephole final : public DfgVisitor {
// If undriven, or driven from another var, it is completely redundant.
if (!vtxp->srcp() || vtxp->srcp()->is<DfgVertexVar>()) {
APPLYING(REMOVE_VAR) {
addSourcesToWorkList(vtxp);
deleteVertex(vtxp);
return;
}
@ -1873,6 +1887,7 @@ class V3DfgPeephole final : public DfgVisitor {
});
if (!keep) {
APPLYING(REMOVE_VAR) {
addSourcesToWorkList(vtxp);
deleteVertex(vtxp);
return;
}
@ -1899,6 +1914,11 @@ class V3DfgPeephole final : public DfgVisitor {
m_workList.foreach([&](DfgVertex& vtx) {
// Remove unused operations as we go. Some vars may be removed in the visit method.
if (!vtx.hasSinks() && !vtx.is<DfgVertexVar>()) {
if (vtx.nInputs()) {
addSourcesToWorkList(&vtx);
m_cache.invalidateByValue(&vtx);
vtx.resetInputs();
}
deleteVertex(&vtx);
return;
}